The present invention relates to a valve assembly that allows trapped air to be expelled from a hydraulic system while substantially preventing hydraulic fluid from being expelled from system. Additionally, the disclosed check valve closes tightly to reduce or prevent the entry of air into the system.
Skill U.S. Pat. No. 6,247,487 discloses a valve assembly having two opposed check valves. One of the two check valves is biased to the closed position, while the other is free to move without any biasing force. The described valve assembly is said to allow gas but not hydraulic fluid to pass through the valve in a first direction, while preventing both gas and hydraulic fluid from passing through the valve in the reverse direction. However, in some cases the valve described in the Skill patent has been found to close prematurely, while substantial air remains in the hydraulic system. This can degrade operation of the hydraulic system.
Kettnich U.S. Pat. No. 2,101,316, Venning U.S. Pat. No. 2,544,476, and Kim U.S. Pat. No. 5,927,315 illustrate other venting, relief, or leakage prevention valves.
By way of general introduction, the valve assembly described below and shown in the drawings includes oppositely facing valve seats that cooperate with respective first and second valve elements. The valve seats are spaced sufficiently closely together that the first valve element, when positioned against the first valve seat, holds the second valve element away from the second valve seat. A spring simultaneously biases the first valve element to the closed position and the second valve element to the open position. In this way, premature closing of the second valve element can be reduced or eliminated, thereby allowing more complete ejection of air and other gases from the hydraulic system.
This section has been provided as an introduction, and it is not intended to narrow the scope of the following claims.